Hi:
I don't have access to the approach charts at the airport in question. Can you please tell me what the lowest glide slope intercept altitude is at the airport?
In the USA, if you have passed the final approach fix, or in the case of an ILS the lowest GS intercept YOU may proceed on the approach if the wx goes down below minimums and you may land IF ALL THE REQUIREMENTS FOR THE APPROACH are met upon reaching DH (DA) (cat 1 or 2). This may be the 1000' business , but again I don't have the charts.
Also, by any stretch of the imagination, was the fog over just the RVR transmissometers and NOT over the runway itself? I've been in a situation of a very localized fog , covering the transmissometers giving a below mins report...however the runway itself was quite clear and in sight 5 miles out. We made a pilot report (pirep) of visbility 3 miles plus and landed all with relatively good respect for the regulations. This was at KPIT.
Having asked these questions in order to give the pilots every benefit of the doubt, it still sounds like they "busted mins" and :
if they had crashed, additional grief would come from the CAA.
if they didn't crash, they will probably "get away with it".
also, who knows, the airline in question may have some special relief in their ops specs for this situation. (thought I doubt it). For example in chicago, at Midway airport, Southwest had a special instrument approach procedure authorizing lower than standard mins...this seemed to factor into the december over run.
regards
jon